$ F = \left[\begin{array}{rrr}2 & 1 & 1 \\ 2 & 0 & 2 \\ 1 & 2 & 0\end{array}\right]$ What is $ F^{-1}$ ?
Explanation: $ = \left[\begin{array}{rrr}2 & -1 & -1 \\ -1 & \frac{1}{2} & 1 \\ -2 & \frac{3}{2} & 1\end{array}\right]$